Systems And Methods For Wavelet Transform Using Mean-Adjusted Wavelets

• US 20110306858A1
• Filed: 06/10/2010
• Published: 12/15/2011
• Est. Priority Date: 06/10/2010
• Status: Abandoned Application

• Current Assignee: Nellcor Puritan Bennett Ireland
• Original Assignee: Nellcor Puritan Bennett Ireland
• Inventors: Watson, James N., Addison, Paul Stanley, Jacquel, Dominique
• Application Number:
  US12/797,747
• Publication Number:
  US 20110306858A1
• Time in Patent Office: Days
• US Class Current: 600/323
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters
• CPC Class Codes: A61B 5/726 using Wavelet transforms
• CPC Class Codes: G06F 17/148 Wavelet transforms

Abstract

Methods and systems are disclosed for transforming a signal using a continuous wavelet transform based at least in part on a truncated, mean-adjusted wavelet. A wavelet may be truncated to a finite support to generate a truncated wavelet. The real part of the truncated wavelet may be forced to have a zero mean to generate a truncated, mean-adjusted wavelet. The signal may be transformed using a continuous wavelet transform based at least in part on the truncated mean-adjusted wavelet. Information may be derived about the signal from the transformed signal.

Claims

1. A method for transforming a signal using a continuous wavelet transform, the method comprising:

generating, using electronic processing equipment, a truncated wavelet from an original wavelet, wherein at least part of the truncated wavelet has a non-zero mean;

forcing, using the electronic processing equipment, the mean of the part of the truncated wavelet to zero to generate a mean-adjusted wavelet; and

performing, using the electronic processing equipment, the continuous wavelet transform on the signal using the mean-adjusted wavelet to generate a transformed signal.

2. The method of claim 1, wherein the part of the truncated wavelet comprises the real part, and/or the imaginary part, and/or a combination thereof.

3. The method of claim 1, wherein generating a truncated wavelet comprises:

forcing, using the electronic processing equipment, the edge values of the wavelet to zero.

4. The method of claim 1, wherein generating a truncated wavelet comprises:

applying, using the electronic processing equipment, a Gaussian envelope to the original wavelet.

5. The method of claim 1, wherein the original wavelet comprises a Morlet wavelet.

6. The method of claim 1, wherein performing the continuous wavelet transform comprises performing a Fast Fourier Transform (FFT)-based method using the electronic processing equipment.

7. The method of claim 1, wherein the signal is a photoplethysmograph signal.

8. The method of claim 1, wherein forcing the mean of the part of the truncated wavelet to zero comprises:

removing the mean value, using the electronic processing equipment, from the part of the truncated wavelet.

9. A system for transforming a signal using a continuous wavelet transform, the system comprising:

an electronic processing equipment configured to;

generate a truncated wavelet from an original wavelet, wherein a part of the truncated wavelet has a non-zero mean;

force the mean of at least part of the truncated wavelet to zero to generate a mean-adjusted wavelet; and

perform the continuous wavelet transform on the signal using the mean-adjusted wavelet to generate a transformed signal.

10. The system of claim 9, wherein the part of the truncated wavelet comprises the real part, and/or the imaginary part, and/or a combination thereof.

11. The system of claim 9, wherein generating a truncated wavelet comprises:

forcing, using the electronic processing equipment, the edge values of the wavelet to zero.

12. The system of claim 9, wherein generating a truncated wavelet comprises:

applying, using the electronic processing equipment, a Gaussian envelope to the original wavelet.

13. The system of claim 9, wherein the original wavelet comprises a Morlet wavelet.

14. The system of claim 9, wherein performing the continuous wavelet transform comprises performing a Fast Fourier Transform (FFT)-based method.

15. The system of claim 9, wherein the signal is a photoplethysmograph signal.

16. The system of claim 9, wherein forcing the mean of the part of the truncated wavelet to zero comprises:

removing the mean value, using the electronic processing equipment, from the part of the truncated wavelet.

17. A method for determining physiological information from a photoplethysmograph (PPG) signal, the method comprising:

collecting the PPG signal using an oximeter;

transforming using electronic processing equipment the PPG signal based at least in part on a continuous wavelet transform wherein the transforming comprises;

truncating a wavelet to generate a truncated wavelet,

forcing the mean of at least part of the truncated wavelet to zero to generate a mean-adjusted wavelet, and

generating a wavelet transform of the PPG signal using the mean-adjusted wavelet; and

determining, using the electronic processing equipment, the physiological information based at least in part on the wavelet transform of the PPG signal.

18. The method of claim 17, wherein the part of the truncated wavelet comprises the real part, and/or the imaginary part, and/or a combination thereof.

19. The method of claim 17, wherein generating a truncated wavelet comprises:

forcing, using the electronic processing equipment, the edge values of the wavelet to zero.

20. The method of claim 17, wherein forcing the mean of the part of the truncated wavelet to zero comprises:

removing the mean value from the part of the truncated wavelet.